Two basic oil-less types of air compressors are known. They are the rotary vane and the wobl. Below follows a summary of modern versions of these compressor types and their drawbacks.
U.S. Pat. No. 4,859,162 (1989) to Cox discloses an improved rotary vane compressor. Materials engineering improvements include a cast iron rotor housing and rotor, and a plastic liner in the housing. However, high heat in the resultant compressed air is still a basic design flaw to this type of compressor. Additional disadvantages include a maximum running life of approximately 8,000 hours, heavy-weight, dust in the output air, noise, high power consumption, and low 15 p.s.i. output.
U.S. Pat. No. 3,961,868 (1976) to Droege, Sr. et al. discloses a wobl type compressor having a traditional flexible piston head. The improvement comprises a Teflon disk, an aluminum cylinder wall having an anodic coating, and an absence of lubrication. However, traditional drawbacks of a basic wobl design include shaking, noise, heavy weight, heat, large size, 7-9000 hours useful life and low 15 p.s.i. output.
U.S. Pat. No. 3,961,869 (1976) to Droege, Sr. et al. improves upon the above noted-patent with a cylinder head and O-ring.
The present invention provides vastly improved operating characteristics for a compressor. The useful life exceeds 50,000 hours for a 1-50 Standard Cubic Feet per Minute volumetric output in the 10 p.s.i. to 120 p.s.i. gauge pressure output range.
To envision the invention take two quarters (circular disks) and tilt them against one another. As you rotate them simultaneously and at different planes of rotation, you will notice that any two adjacent points move in an oscillatory motion toward and away from one another. Therefore, if one quarter holds a piston and the other quarter holds a cylinder, then you have an oscillating piston in a cylinder. Add valves and you have a compressor. Further efficiencies are gained when a third synchronously rotating disk is added at the same off axis angle as the first two disks. The central disk holds opposing pistons, thereby counter balancing vibration forces from each piston. The outer disks consist of cylinder housings. A maximum weight and size efficiency is achieved with a pair of six cylinder outer housings and a central disk having twelve pistons, six each facing toward its matching cylinder.
The above described principles have been used in high pressure hydraulic compressors and motors. They have come to be known as axial piston devices. The hydraulic axial piston devices noted below are all encased in pressure resistant housings, are all internally rotated through their central axes, and are all low speed, high pressure, small cylinder devices. They are not suited for a high speed, low pressure, large cylinder design needed for gas (air) compressors.
Below follows a summary of the hydraulic axial piston device prior art.
U.S. Pat. No. 2,875,701 (1959) to Ebert discloses a hydrostatic piston engine (used as a pump or a motor) using the concept of axially arranged pistons. These pistons rotate off axis with respect to axially arranged cylinders. The improvement consists of using interconnected chambers between the opposing pistons as pressure equalizing devices. FIG. 1 teaches the axial limit of the cylinder housings axes are located above the axial piston housing central axis. This design feature is used in the present invention. This design feature allows for large pistons and corresponding high volume compressor outputs. Ebert, however, does not utilize this design feature to provide for large diameter pistons and cylinders. Large diameter pistons and cylinders are essential for gas compressors. This particular design feature represents the closest known prior art.
U.S. Pat. No. 3,052,098 (1962) to Ebert discloses an infinitely variable torque transmission having a series of axially offset piston/cylinder units including at least one pump and at least two motors.
U.S. Pat. No. 3,434,429 (1969) to Goodwin discloses a hydraulic pump of the axial piston type. A first cylinder block is rotated by a drive shaft. The first cylinder block turns a drive shaft which turns a second cylinder block having a non-parallel housing of axial rotation. Opposing pistons are rotating synchronously between the two cylinder blocks, thereby forming a pumping action by moving in the cylinders which are housed in the cylinder blocks. There exists a passage extending axially through each of the piston rods allowing fluid passage to and from the opposing cylinders.
U.S. Pat. No. 4,361,177 (1982) to Mills discloses an axial piston type variable positive displacement fluid motor/pump. The piston rods are double ended and held axially stationary with respect to the main shaft. The cylinder barrels have a variable axis of rotation enabling a variable torque output. Further, distinct high pressure and low pressure chambers are used.
U.S. Pat. No. 2,821,932 (1958) to Lucien discloses a swash plate fluid pressure pump. The fluid pressure pump (or motor) comprises a casing having inlet and outlet ports. Parallel cylinders have pistons movable in the cylinders. A rotatable plate has on one side a planar surface perpendicular to the driving shaft and, on the other side, an inclined surface. Rotating the rotatable plate moves the pistons in the cylinders.
U.S. Pat. No. 2,956,845 (1960) to Wahlmark discloses a hydraulic device with a swash plate comprising piston members with a spherically surfaced member.
U.S. Pat. No. 3,289,604 (1966) to Wahlmark discloses a hydraulic device with a swash plate. Both axial and radial loading to the plate are absorbed with a drive shaft overhang arrangement.
U.S. Pat. No. 3,180,275 (1965) to Boulet discloses a hydraulic engine of the rotary barrel type. Each piston has movement parallel to a driving shaft for cylindrical movement.
U.S. Pat. No. 3,196,801 (1965) to Ifield discloses a hydraulic liquid axial piston pump (or motor) with an adjustable inclined plate for providing variable displacement. The piston assembly rotates on a universal joint. The rotating cylinder plate is adjustably movable.
U.S. Pat. No. 2,146,133 (1939) to Tweedale discloses a fluid pressure power transmission having a series of piston/cylinder units at an angle moving with a rotary plate.
U.S. Pat. No. 2,556,585 (1951) to Jarvinen discloses an internal-combustion motor with a cylinder arranged concentrically about and parallel with the driveshaft. The motor is lubricated and cooled by fluids.
Russian 142,487 (1960) to Tyarason discloses an axial piston pump for fluids differing in the fact that bent pipes and tie rods relieve tensile forces, and torroidal chambers reduce inertia.
The present invention improves upon the prior art by providing a free standing, caseless, set of rotating cylinder housings and a central rotating piston disk. A stationary mounting spindle passes through the spin axes of all three of the aforementioned rotating disk and housings. This design also incorporates raising the axial limit of the rotating cylinder housings above the central axis of the rotating piston disk. This design allows large pistons to be mounted on the rotating piston disk and likewise allows large cylinders to be contained within the rotating cylinder housings. The stationary mounting spindle absorbs the central thrust vector and all the corresponding compression forces.
The spin rotation is provided exteriorly on the periphery of the rotating piston disk. Spin rotation is synchronously transmitted to the adjacent rotating cylinder housings by means of gears. The resultant design enables an oil-less 1700 rpm air compressor to provide 120 p.s.i. in excess of 50,000 hours.